NCERT Solutions for Class 8 Science Chapter 18 Pollution - Air and Water

This is again an important chapter related to our planet. Students will learn in detail about climate warming, the greenhouse effect and acid rain. There is a case study on the harmful effects of pollution on the Taj Mahal and how it got exposed to marble cancer. This is due to the pollution from industries and oil refineries near Agra.

Students will also be asked to consider ways of how they can help combat air and water pollution in their individual capacities.

Download PDF of NCERT Solutions for Class 8 Science Chapter 18 Pollution - Air and Water

Question: 1. What are the different ways in which water gets contaminated ?

Answer 1 – The degradation of water quality or water pollution is caused by the disposal of domestic sewage, chemicals present in fertilizers and pesticides, and chemicals released in water bodies from industries as waste.

Question: 2. At an individual level, how can you help reduce air pollution?

Answer 2 - Air pollution can be reduced by taking the following measures;

1. Avoid burning fossil fuels like coal for domestic purposes.

2. Using public transport and bicycles for commuting.

3. Planting plenty of trees which purify the air.

4. Avoid using equipment in gardens that use gas.

Question: 3. Clear, transparent water is always fit for drinking. Comment.

Answer 3 - Water that is clear and transparent is not necessarily safe to drink. Although water may appear to be free of disease-causing microorganisms, it may contain some. As a result, purifying water before drinking is recommended.

Question: 4. You are a member of the municipal body of your town. Make a list of measures that would help your town to ensure the supply of clean water to all its residents.

Answer 4 –

• Ban using and throwing polythene bags in water bodies.

• Purifying water using chlorine.

• Regular cleaning and disinfecting of water pipes.

• Not allowing open defecation near and inside water bodies.

Question: 5. Explain the differences between pure air and polluted air.

Answer 5 -

Pure air	Polluted air
Fitr for breathing.	Unfit for breathing.
Contains essential gases like nitrogen (78% ), oxygen (21%), and carbon dioxide (0.03%) in balanced and definite proportions.	Polluted air does not have this balanced composition of gases as it has harmful pollutants as well.

Question: 6. Explain circumstances leading to acid rain. How does acid rain affect us?

Answer 6 - Acid rain is caused by the combustion of fossil fuels which releases a number of pollutants into the atmosphere, including sulphur dioxide and nitrogen. When they interact with water, they produce Acid rain's adverse impacts such as,

Effects of acid rain:

1. Acid rain irritates the skin.

2. It affects the soil's fertility and damage crops.

3. Plant germination is hindered.

4. Plants and aquatic life are destroyed.

5. It corrodes buildings, historical monuments, and bridges.

Question: 7. Which of the following is not a greenhouse gas?

Answer 7 – Nitrogen is not a greenhouse gas as it does not increase Earth’s temperature.

Carbon dioxide, sulphur dioxide, and methane are greenhouse gases as the increase in their levels on Earth’s surface increases the temperature and causes global warming.

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Question: 8. Describe the ‘Green House Effect’ in your own words.

Answer 8 - The greenhouse effect is a rise in Earth's temperature caused by increased levels of greenhouse gases in the atmosphere such as carbon dioxide, methane, and water vapour. As a result, these greenhouse gasses trap radiation from the sun that is reflected by the Earth.

Question: 9. Prepare a brief speech on global warming. You have to deliver the speech in your class.

Answer 9- Global warming is defined as an increase in the average temperature of the Earth's surface. It arises as a result of rising levels of greenhouse gases in the environment. Carbon dioxide, methane, and sulphur dioxide are examples of some greenhouse gases.

These gases capture the rays from the sun that the earth reflects, which helps to maintain optimum temperature to survive on Earth. But a rise in these gases can result in global warming by raising the earth's temperature which melts glaciers causing mass destruction by floods, tsunamis, and droughts.

Question: 10. Describe the threat to the beauty of the Taj Mahal.

Answer 10 - Acid rain is a severe threat to the Taj Mahal's splendour. Marble which is calcium carbonate has been used for the construction of the monument.

When acid rain falls on the monument, the marble interacts with the acid, forming a powdery residue that is rinsed away by the rain. In addition, soot particles generated from the oil refinery in Agra are causing the Taj Mahal's marble to yellow.

Question: 11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

Answer 11 – Sources such as factories, households, and agricultural run-offs contain harmful compounds which promote excessive growth of algae. This is known as an algal bloom. This algal growth consumes huge levels of dissolved oxygen present in the water resulting in the decrease in oxygen levels required for the survival of aquatic life.

The availability of less oxygen for aquatic plants and animals leads to their death. This disturbs the balance in the aquatic lives.

Links to Other Resources for Class 8 Science

Other Class 8 Science Related Links
Understanding Structure and Functions of a Cell
Deforestation, Afforestation and Reforestation
Frictional Force Definition, and Types with Example
Compare LPG and Wood as Fuel
Water Pollution Causes and Effects with Example